Unfortunately, the transition to the construction of combined cycle CHPPs (CCGT CHPPs) instead of steam turbines has led to even more sharp decline district heating in the overall energy production. This, in turn, leads to an increase in the energy intensity of GDP and a decrease in the competitiveness of domestic products, as well as an increase in the cost of housing and communal services.

¦ high efficiency of electricity generation at the CCGT CHPP according to the condensation cycle up to 60%;

¦ Difficulties in locating CCGT CHPPs in conditions of dense urban development, as well as an increase in fuel supplies to cities;

¦ According to the established tradition, CCGT CHPPs are equipped, as well as steam turbine stations, with T-type cogeneration turbines.

Construction of a CHP plant with P-type turbines since the 1990s. the last century, was practically discontinued. In pre-perestroika times, industrial enterprises accounted for about 60% of the heat load in cities. Their need for heat for the implementation of technological processes during the year was quite stable. During the hours of morning and evening peaks in urban power consumption, power supply peaks were smoothed out by introducing appropriate regimes for limiting the supply of electrical energy to industrial enterprises. The installation of P-type turbines at the CHPP was economically justified due to their lower cost and more efficient use of energy resources compared to T-type turbines.

The last 20 years due to a sharp decline industrial production the mode of energy supply of cities has changed significantly. Currently, city CHPPs operate according to the heating schedule, in which the summer heat load is only 15-20% calculated value. The daily schedule of electricity consumption has become more uneven due to the inclusion of electrical load by the population in the evening hours, which is associated with a massive increase in the supply of electricity to the population. household appliances. In addition, leveling the energy consumption schedule by introducing appropriate restrictions on industrial consumers due to their small share in total energy consumption turned out to be impossible. The only one not very effective way The solution to the problem was the reduction of the evening maximum due to the introduction of reduced tariffs at night.

Therefore, in steam turbine CHP plants with P-type turbines, where the generation of thermal and electrical energy is strictly interconnected, the use of such turbines turned out to be unprofitable. Backpressure turbines are now produced only at low power to improve the efficiency of urban steam boilers by switching them to cogeneration mode.

Such an established approach was also preserved at the construction of the CCGT CHPP. At the same time, there is no rigid relationship between the supply of heat and electricity in the combined cycle. At these stations with turbines of the P type, the coverage of the evening maximum electrical load can be carried out by temporarily increasing the supply of electricity in the gas turbine cycle. A short-term decrease in heat supply to the heat supply system does not affect the quality of heating due to the heat storage capacity of buildings and the heating network.

The schematic diagram of the CCGT CHPP with counterpressure turbines includes two gas turbines, a waste heat boiler, a P-type turbine, and a peak boiler (Fig. 2). The peak boiler, which can be installed outside the CCGT site, is not shown in the diagram.

From fig. 2, it can be seen that the CCGT CHPP consists of a gas turbine plant consisting of a compressor 1, a combustion chamber 2 and a gas turbine 3. heat exchangers in which the water is heated, the steam is separated in the drums of low 7 and high pressure 8, is sent to the steam turbine unit (STU) 11. Moreover, saturated steam low pressure enters the intermediate compartment of the STP, and the high-pressure steam is preliminarily superheated in the waste heat boiler and sent to the head of the STP. The steam leaving the STP is condensed in the heating water heat exchanger 12 and is sent to the gas condensate heater 14 by condensate pumps 13, and then sent to the deaerator 9 and from him in KU.

With a thermal load not exceeding the base one, the station operates completely according to the heating schedule (ATES=1). If the heat load exceeds the base load, the peak boiler is switched on. The required amount of electricity comes from external sources of generation through the city's power grids.

However, situations are possible when the demand for electricity exceeds the volume of its supply from external sources: on frosty days with an increase in electricity consumption by household heating appliances; in case of accidents at generating facilities and in electrical networks. In such situations, the capacity of gas turbines in the traditional approach is closely related to the performance of the waste heat boiler, which in turn is dictated by the need for thermal energy in accordance with the heating schedule and may not be sufficient to meet the increased demand for electricity.

In order to cover the shortage of electricity that has arisen, the gas turbine switches partially to the discharge of waste combustion products, in addition to the waste heat boiler, directly into the atmosphere. Thus, the CCGT CHPP is temporarily transferred to a mixed mode - with combined cycle and gas turbine cycles.

It is known that gas turbine plants have high maneuverability (the rate of gain and loss of electrical power). Therefore, even in Soviet time they were supposed to be used, along with pumped-storage stations, to smooth the power supply regime.

In addition, it should be noted that the power developed by them increases with a decrease in the outdoor temperature and it is at low temperatures during the coldest time of the year, the maximum power consumption is observed. This is shown in the table.

When the power reaches more than 60% of the calculated value, emissions of harmful gases NOx and CO are minimal (Fig. 3).

In the non-heating period, in order to prevent a decrease in the power of gas turbines by more than 40%, one of them is turned off.

Increasing the energy efficiency of CHPPs can be achieved through centralized refrigeration supply to urban microdistricts. In emergency situations at the CCGT CHPP, it is advisable to build gas turbine units of low power in separate buildings.

In areas of dense urban development of large cities, when reconstructing existing CHPPs with exhausted steam turbines, it is advisable to create on their basis a CCGT CHPP with R-type turbines. As a result, significant areas occupied by the cooling system (cooling towers, etc.) are freed up, which can be used for other purposes.

Comparison of CCGT CHP with backpressure turbines (P type) and CCGT CHP with condensate extraction turbines (T type) allows us to make the following conclusions.

  • 1. In both cases, the fuel efficiency depends on the share of electricity generation based on heat consumption in the total generation volume.
  • 2. In CCGT CHPPs with turbines of type T, heat losses in the condensate cooling circuit occur throughout the year; the greatest losses in summer period when the amount of heat consumption is limited only to hot water supply.
  • 3. In CCGT CHPPs with turbines of the R type, the efficiency of the plant decreases only for a limited period of time, when it is necessary to cover the shortage in electricity supply.
  • 4. Maneuvering characteristics (speeds of loading and unloading) of gas turbines are many times higher than those of steam turbines.

Thus, for the conditions of construction of stations in the centers big cities CCGT CHPPs with counterpressure turbines (P type) outperform combined cycle CHP plants with condensate extraction turbines (T type) in all respects. They require a much smaller area to accommodate, they are more economical in terms of fuel consumption and their environmental impact is also less.

However, for this it is necessary to make appropriate changes to the regulatory framework for the design of combined cycle plants.

Practice recent years shows that investors constructing out-of-town CCGT CHPPs and in fairly free territories give priority to electricity generation, and heat supply is considered by them as a side activity. This is explained by the fact that the efficiency of stations, even in the condensing mode, can reach 60%, and the construction of heating mains requires additional costs and numerous agreements with different structures. As a result, the heat supply coefficient of the CHPP can be less than 0.3.

Therefore, when designing a CCGT CHPP, it is not advisable for each individual plant to include in the technical solution the optimal value of ATES. The task is to find the optimal share of district heating in the heat supply system of the entire city.

Now the concept of building powerful thermal power plants in places where fuel is extracted, far from big cities, developed in Soviet times, has again become relevant. This is dictated both by an increase in the share of using local fuels in the fuel and energy complex of the regions, and by the creation of new designs of heat pipelines (air laying) with an almost negligible drop in the temperature potential during the transportation of the coolant.

Such thermal power plants can be created both on the basis of a steam turbine cycle with direct combustion of local fuel, and a combined cycle with the use of gas produced at gas generators.


To thermal power plants(CHP) include power plants that generate and supply consumers not only electricity, but also thermal energy. In this case, steam from intermediate turbine extractions, partially already used in the first stages of turbine expansion for generating electricity, as well as hot water with a temperature of 100-150 ° C, heated by steam taken from the turbine, serve as heat carriers. Steam from a steam boiler enters the turbine through a steam pipeline, where it expands to the pressure in the condenser and its potential energy is converted into mechanical work of rotation of the turbine rotor and the generator rotor connected to it. Part of the steam after several stages of expansion is taken from the turbine and sent through the steam pipeline to the steam consumer. The place of steam extraction, and hence its parameters, are set taking into account the requirements of the consumer. Since the heat at the CHP is spent on the production of electrical and thermal energy, the efficiency of the CHP for the production and supply of electricity and the production and supply of heat differ.

Gas turbine plants(GTP) consist of three main elements: an air compressor, a combustion chamber and a gas turbine. Air from the atmosphere enters the compressor, driven by the starting motor, and is compressed. Then, under pressure, it is fed into the combustion chamber, where liquid or gaseous fuel is simultaneously supplied by a fuel pump. In order to reduce the gas temperature to an acceptable level (750-770°C), 3.5-4.5 times more air is fed into the combustion chamber than is necessary for fuel combustion. In the combustion chamber, it is divided into two streams: one stream enters the flame tube and ensures complete combustion of the fuel, and the second flows around the flame tube from the outside and, mixing with the combustion products, reduces their temperature. After the combustion chamber, the gases enter the gas turbine, which is located on the same shaft as the compressor and generator. There, they expand (to about atmospheric pressure), do work by rotating the turbine shaft, and then are ejected through the chimney. The power of a gas turbine is much less than the power of a steam turbine and at present the efficiency is about 30%.

Combined-cycle plants(CCP) are a combination of steam turbine (STU) and gas turbine (GTU) installations. Such a combination makes it possible to reduce the waste heat losses of gas turbines or the heat of exhaust gases of steam boilers, which ensures an increase in efficiency compared to separately taken STPs and GTPs. In addition, with such a combination, a number of design advantages are achieved, leading to a reduction in the cost of the installation. Two types of CCGT are widely used: those with high-pressure boilers and those with discharge of turbine exhaust gases into the combustion chamber of a conventional boiler. The high-pressure boiler runs on gas or purified liquid fuel. Flue gases leaving the boiler with high temperature and overpressure are directed to the gas turbine, on the same shaft with which there are a compressor and a generator. The compressor pumps air into the combustion chamber of the boiler. The steam from the high-pressure boiler is directed to the condensing turbine, which has a generator on the same shaft. The steam exhausted in the turbine passes into the condenser and, after condensation, is pumped back into the boiler by a pump. Turbine exhaust gases are fed to the economizer to heat the boiler feed water. In such a scheme, a smoke exhauster is not required to remove the flue gases of a high-pressure boiler, the compressor performs the function of a blast pump. The efficiency of the installation as a whole reaches 42-43%. In another scheme of the combined cycle plant, the heat of the exhaust gases of the turbine in the boiler is used. The possibility of discharge of exhaust gases from the turbine into the combustion chamber of the boiler is based on the fact that in the combustion chamber of the gas turbine the fuel (gas) is burned with a large excess of air and the oxygen content in the exhaust gases (16-18%) is sufficient to burn the bulk of the fuel.



29. NPP: device, types of reactors, parameters, operating characteristics.

Nuclear power plants are thermal power plants, because in their device there are heat emitters, a coolant and an electric generator. current - turbine.

Nuclear power plants can be condensing, heating plants (ATES), nuclear heat supply stations (AST).

Nuclear reactors are classified according to various criteria:

1. according to the neutron energy level:

On thermal neutrons

On fast neutrons

2. according to the type of neutron moderator: water, heavy water, graphite.

3. by type of coolant: water, heavy water, gas, liquid metal

4. by the number of circuits: one-, two-, three-circuit

In modern reactors for the fission of nuclei of the original fuel, mainly thermal neutrons are used. All of them have, first of all, the so-called core, into which nuclear fuel containing uranium 235 is loaded moderator(usually graphite or water). To reduce the leakage of neutrons from the core, the latter is surrounded reflector , usually made of the same material as the moderator.

Behind the reflector outside the reactor is placed concrete protection from radioactive radiation. Loading of the reactor with nuclear fuel usually considerably exceeds the critical one. In order to continuously maintain the reactor in a critical state as the fuel burns out, a strong neutron absorber in the form of boron carbamide rods is introduced into the core. Such rods called governing or compensatory. During nuclear fission, a large number of heat that is removed coolant into the heat exchanger steam generator, where it turns into a working fluid - steam. The steam enters turbine and rotates its rotor, the shaft of which is connected to the shaft generator. The exhaust steam in the turbine enters capacitor, after which the condensed water again goes to the heat exchanger, and the cycle repeats.

combined-cycle are called power plants (PSU), in which the heat of the exhaust gases of the gas turbine is directly or indirectly used to generate electricity in the steam turbine cycle.

On fig. 4.10 shows a schematic diagram of the simplest combined-cycle plant, the so-called utilization type. Outgoing gases from the gas turbine are fed into waste heat boiler- a counterflow type heat exchanger, in which, due to the heat of hot gases, steam of high parameters is obtained, which is directed to a steam turbine.

Figure 4.10. Schematic diagram of the simplest combined cycle plant

The waste heat boiler is a rectangular shaft, in which heating surfaces are located, formed by ribbed pipes, inside which the working fluid is supplied steam turbine plant(water or steam). In the simplest case, the heating surfaces of the waste heat boiler consist of three elements: economizer 3, evaporator 2, and superheater 1. The central element is the evaporator, consisting of a drum 4 (a long cylinder half-filled with water), several downcomers 7 and rather densely installed vertical pipes of the evaporator 8 itself. The evaporator works on the principle of natural convection. The evaporator pipes are located in the zone of higher temperatures than the downcomers. Therefore, in them, the water heats up, partially evaporates and therefore becomes lighter and rises up into the drum. The vacated space is filled with colder water through downpipes from the drum. Saturated steam is collected in the upper part of the drum and sent to the pipes of the superheater 1. The steam flow from the drum 4 is compensated by the supply of water from the economizer 3. In this case, the incoming water, before completely evaporating, will repeatedly pass through the evaporation pipes. Therefore, the described waste heat boiler is called boiler with natural circulation.

In the economizer, the incoming feed water is heated almost to the boiling point. From the drum, dry saturated steam enters the superheater, where it is superheated above the saturation temperature. The temperature of the resulting superheated steam t 0 is always, of course, less than the temperature of the gases q G coming from the gas turbine (usually 25 - 30 °C).

Under the scheme of the waste heat boiler in fig. 4.10 shows the change in the temperatures of the gases and the working fluid as they move towards each other. The temperature of the gases gradually decreases from the value q Г at the inlet to the value q ux of the temperature of the exhaust gases. moving towards Feed water raises its temperature in the economizer to the boiling point(dot A). With this temperature (on the verge of boiling), water enters the evaporator. It evaporates water. At the same time, its temperature does not change (process a - b). At the point b the working fluid is in the form of a dry saturated steam. Further, in the superheater, it overheats to a value t 0 .

The steam formed at the outlet of the superheater is sent to the steam turbine, where, expanding, it does work. From the turbine, the exhaust steam enters the condenser, condenses and with the help of a feed pump 6 , which increases the pressure of the feed water, is sent back to the waste heat boiler.

Thus, the fundamental difference between a steam power plant (SPU) of a CCGT and a conventional CCP of a TPP is only that the fuel is not burned in the waste heat boiler, and the heat necessary for the operation of the CCGT CCGT is taken from the exhaust gases of the gas turbine. General form waste heat boiler is shown in Figure 4.11.

Figure 4.11. General view of the waste heat boiler

The power plant with CCGT is shown in fig. 4.12, which shows a TPP with three power units. Each power unit consists of two adjacent gas turbines 4 type V94.2 Siemens, each of which has its own exhaust gases high temperature sends to its waste heat boiler 8 . The steam generated by these boilers is sent to one steam turbine 10 with electric generator 9 and a condenser located in the condensation room under the turbine. Each such power unit has a total capacity of 450 MW (each gas turbine and steam turbine has a capacity of approximately 150 MW). Between outlet diffuser 5 and waste heat boiler 8 installed bypass (bypass) chimney 12 and gas-tight gate 6 .

Figure 4.12. Power plant with CCGT

The main advantages of PGU.

1. Combined-cycle plant is currently the most economical engine used to generate electricity.

2. Combined-cycle plant is the most environmentally friendly engine. First of all, this is due to the high efficiency - after all, all the heat contained in the fuel, which could not be converted into electricity, is released into the environment and its thermal pollution occurs. Therefore, the reduction in thermal emissions from a CCGT compared to a steam power plant approximately corresponds to a decrease in fuel consumption for electricity generation.

3. Combined-cycle plant is a very maneuverable engine, which can only be compared in maneuverability by an autonomous gas turbine. Potentially high maneuverability of the PTU is ensured by the presence of a GTP in its scheme, the load change of which occurs within a few minutes.

4. With the same capacity of steam-powered and combined-cycle TPPs, the consumption of CCGT cooling water is approximately three times less. This is determined by the fact that the power of the steam-power part of the CCGT is 1/3 of the total power, and the GTU practically does not require cooling water.

5. The CCGT has a lower cost per installed unit of capacity, which is associated with a smaller volume of the construction part, the absence of a complex power boiler, an expensive chimney, a regenerative feedwater heating system, the use of a simpler steam turbine and a service water supply system.

CONCLUSION

The main disadvantage of all thermal power plants is that all types of fuel used are irreplaceable. natural resources which are gradually ending. In addition, thermal power plants consume a significant amount of fuel (every day one GRES with a capacity of 2000 MW burns two railway trains of coal per day) and are the most environmentally “dirty” sources of electricity, especially if they operate on high-ash sulfur fuels. That is why at present, along with the use of nuclear and hydraulic power plants, the development of power plants using renewable or other alternative energy sources is underway. However, in spite of everything, thermal power plants are the main producers of electricity in most countries of the world and will remain so for at least the next 50 years.

CONTROL QUESTIONS FOR LECTURE 4

1. Thermal scheme of CHPP - 3 points.

2. Technological process electricity generation at thermal power plants - 3 points.

3. The layout of modern thermal power plants - 3 points.

4. Features of GTU. Structural diagram of the GTU. GTU efficiency - 3 points.

5. Thermal diagram of the gas turbine - 3 points.

6. Features of CCGT. Structural scheme of PGUU. CCGT efficiency - 3 points.

7. Thermal diagram of CCGT - 3 points.


LECTURE 5

NUCLEAR POWER PLANTS. FUEL FOR NPP. OPERATING PRINCIPLE OF A NUCLEAR REACTOR. POWER GENERATION AT NPP WITH THERMAL REACTORS. FAST NEUTRON REACTORS. ADVANTAGES AND DISADVANTAGES OF MODERN NPPs

Basic concepts

Nuclear power plant(NPP) is a power plant, generating electrical energy by converting the thermal energy released in a nuclear reactor (reactors) as a result of a controlled chain reaction of fission (splitting) of the nuclei of uranium atoms. The fundamental difference between a nuclear power plant and a thermal power plant is that instead of a steam generator, a nuclear reactor is used - a device in which a controlled nuclear chain reaction is carried out, accompanied by the release of energy.

The radioactive properties of uranium were first discovered by a French physicist Antoine Becquerel in 1896. English physicist Ernest Rutherford first carried out an artificial nuclear reaction under the action of particles in 1919. German physicists Otto Hahn And Fritz Strassmann opened in 1938 , that the fission of heavy uranium nuclei when bombarded by neutrons accompanied by the release of energy. The actual use of this energy has become a matter of time.

The first nuclear reactor was built in December 1942 in the USA a group of physicists at the University of Chicago led by an Italian physicist Enrico Fermi. The undamped uranium nuclear fission reaction was realized for the first time. The nuclear reactor, called SR-1, consisted of graphite blocks, between which were located balls of natural uranium and its dioxide. Fast neutrons that appear after nuclear fission 235 U, were slowed down by graphite to thermal energies, and then caused new nuclear fission. Reactors in which the main share of fissions occurs under the action of thermal neutrons are called thermal (slow) neutron reactors; in such reactors there is much more moderator than uranium.

In Europe, the first F-1 nuclear reactor was manufactured and launched in December 1946 in Moscow. a group of physicists and engineers headed by Academician Igor Vasilyevich Kurchatov. The F-1 reactor was assembled from graphite blocks and had the shape of a ball with a diameter of approximately 7.5 m. In the central part of the ball with a diameter of 6 m, uranium rods were placed in the holes of the graphite blocks. The F-1 reactor, like the SR-1, did not have a cooling system, so it operated at low power levels: from fractions to units of a watt.

The results of research at the F-1 reactor served as the basis for projects for industrial reactors. In 1948, under the leadership of I. V. Kurchatov, work began on practical application atomic energy to generate electricity.

The world's first industrial nuclear power plant with a capacity of 5 MW was launched on June 27, 1954 in Obninsk Kaluga region . In 1958, the 1st stage of the Siberian NPP was put into operation with a capacity of 100 MW (full design capacity of 600 MW). In the same year, the construction of the Beloyarsk industrial nuclear power plant began, and in April 1964, the generator of the 1st stage provided electricity to consumers. In September 1964, the 1st block of the Novovoronezh NPP with a capacity of 210 MW was launched. The second unit with a capacity of 350 MW was launched in December 1969. In 1973, the Leningrad NPP was launched.

In the UK, the first industrial nuclear power plant with a capacity of 46 MW was commissioned in 1956 at Calder Hall. A year later, a 60 MW nuclear power plant was put into operation in Shippingport (USA).

World leaders in production nuclear electricity are: USA (788.6 billion kWh/year), France (426.8 billion kWh/year), Japan (273.8 billion kWh/year), Germany (158.4 billion kWh/year) ) and Russia (154.7 billion kWh/year). At the beginning of 2004, there were 441 nuclear power reactors operating in the world, the Russian TVEL OJSC supplies fuel for 75 of them.

The largest nuclear power plant in Europe - Zaporozhye NPP, Energodar (Ukraine) - 6 nuclear reactors with a total capacity of 6 GW. The world's largest nuclear power plant - Kashiwazaki-Kariva (Japan) - five boiling nuclear reactors ( BWR) and two advanced boiling water reactors ( ABWR), the total capacity of which is 8.2 GW.

Currently, the following nuclear power plants operate in Russia: Balakovo, Beloyarskaya, Bilibinskaya, Rostovskaya, Kalininskaya, Kola, Kurskaya, Leningradskaya, Novovoronezhskaya, Smolenskaya.

The development of the draft Energy Strategy of Russia for the period up to 2030 provides for an increase in electricity production at nuclear power plants by 4 times.

Nuclear power plants are classified according to the reactors installed on them:

l thermal neutron reactors , using special moderators to increase the probability of absorption of a neutron by the nuclei of fuel atoms;

l fast neutron reactors .

According to the type of energy supplied, nuclear power plants are divided into:

l nuclear power plants(NPP) designed to generate electricity only;

l nuclear combined heat and power plants (ATPPs) that produce both electricity and heat.

Currently, only in Russia are options for the construction of nuclear heat supply stations.

NPP does not use air to oxidize fuel, does not emit ash, sulfur oxides, carbon, etc. into the atmosphere, has a lower radioactive background than at a thermal power plant, but, like a thermal power plant, consumes a huge amount of water to cool the condensers.

Fuel for nuclear power plants

The main difference between a nuclear power plant and a thermal power plant is use of nuclear fuel instead of fossil fuels. Nuclear fuel is obtained from natural uranium, which is mined either in mines (Niger, France, South Africa), or in open pits (Australia, Namibia), or by underground leaching (Canada, Russia, USA). Uranium is widely distributed in nature, but there are no rich deposits of uranium ores. Uranium is found in various rocks and water in a dispersed state. Natural uranium is a mixture of the predominantly non-fissile isotope of uranium 238 U(more than 99%) and fissile isotope 235 U (about 0.71%), which is a nuclear fuel (1 kg 235 U releases energy equal to the calorific value of about 3000 tons of coal).

For the operation of nuclear power plant reactors, uranium enrichment. To do this, natural uranium is sent to an enrichment plant, after processing, where 90% of natural depleted uranium is sent for storage, and 10% is enriched to 3.3 - 4.4%.

From enriched uranium (more precisely, uranium dioxide UO 2 or uranium oxides U 2 O 2) are made fuel elements - fuel rods- cylindrical tablets with a diameter of 9 mm and a height of 15-30 mm. These tablets are placed in airtight zirconium(neutron absorption by zirconium is 32.5 times less than by steel) thin wall tubes about 4 m long. Fuel rods are assembled into fuel assemblies (FA) in several hundred pieces.

All further nuclear fission processes 235 U with the formation of fission fragments, radioactive gases, etc. are happening inside sealed tubes of fuel rods.

After gradual splitting 235 U and reducing its concentration to 1.26%, when the reactor power is significantly reduced, fuel assemblies are removed from the reactor, are stored in the spent fuel pool for some time, and then sent to the radiochemical plant for processing.

Thus, unlike thermal power plants, where they tend to burn fuel completely, it is impossible to split nuclear fuel by 100% at nuclear power plants. Therefore, it is impossible to calculate the efficiency at NPPs based on the specific consumption of standard fuel. To assess the efficiency of the NPP power unit, the net efficiency factor is used

,

where is the generated energy, is the heat released in the reactor at the same time and the same time.

The NPP efficiency calculated in this way is 30–32%, but it is not entirely legitimate to compare it with the TPP efficiency of 37–40%.

In addition to the uranium 235 isotope, the following are also used as nuclear fuel:

  • uranium isotope 233 ( 233 U) ;
  • plutonium isotope 239 ( 239 Pu);
  • thorium isotope 232 ( 232Th) (by converting to 233 U).

How is a CHP set up? CHP units. CHP equipment. CHP operating principles. CCGT-450.

Hello dear ladies and gentlemen!

When I studied at the Moscow Power Engineering Institute, I lacked practice. At the institute, you deal mainly with "pieces of paper", but I rather wanted to see "pieces of iron". It was often difficult to understand how this or that unit works, never having seen it before. The sketches offered to students do not always allow to understand the full picture, and few could imagine the true design, for example, of a steam turbine, considering only the pictures in the book.

This page is designed to fill the existing gap and provide everyone who is interested, if not too detailed, but clear information about how the equipment of the Heat and Electric Central (CHP) is arranged "from the inside". The article considers a fairly new for Russia type of power unit CCGT-450, which uses in its work a combined cycle - combined cycle (most thermal power plants use only a steam cycle so far).

The advantage of this page is that the photographs presented on it were taken at the time of the construction of the power unit, which made it possible to shoot the device of some technological equipment disassembled. In my opinion, this page will be most useful for students of energy specialties - for understanding the essence of the issues being studied, as well as for teachers - for using individual photographs as methodological material.

The source of energy for the operation of this power unit is natural gas. During the combustion of gas, thermal energy is released, which is then used to operate all the equipment of the power unit.

In total, three power machines operate in the power unit scheme: two gas turbines and one steam one. Each of the three machines is designed for a rated electrical power output of 150 MW.

Gas turbines are similar in principle to jet aircraft engines.

Gas turbines require two components to operate: gas and air. Air from the street enters through the air intakes. The air intakes are covered with grilles to protect the gas turbine plant from birds and any debris. They also have an anti-icing system that prevents ice from freezing in the winter.

The air enters the compressor inlet of the gas turbine plant (axial type). After that, in a compressed form, it enters the combustion chambers, where, in addition to air, natural gas is supplied. In total, each gas turbine plant has two combustion chambers. They are located on the sides. In the first photo below, the air duct has not yet been mounted, and the left combustion chamber is closed with a plastic film, in the second, a platform has already been mounted around the combustion chambers, and an electric generator has been installed:

Each combustion chamber has 8 gas burners:

In the combustion chambers, the process of combustion of the gas-air mixture and the release of thermal energy takes place. This is what the combustion chambers look like "from the inside" - just where the flame burns continuously. The walls of the chambers are lined with refractory lining:

At the bottom of the combustion chamber there is a small viewing window that allows you to observe the processes occurring in the combustion chamber. The video below demonstrates the process of combustion of the gas-air mixture in the combustion chamber of a gas turbine plant at the time of its start-up and when operating at 30% of the rated power:

The air compressor and gas turbine are on the same shaft, and part of the turbine's torque is used to drive the compressor.

The turbine produces more work than is required to drive the compressor, and the excess of this work is used to drive the "payload". As such a load, an electric generator with an electric power of 150 MW is used - it is in it that electricity is generated. In the photo below, the "gray barn" is just the electric generator. The generator is also located on the same shaft as the compressor and turbine. All together rotates at a frequency of 3000 rpm.

When passing through a gas turbine, the combustion products give it part of their thermal energy, but not all of the energy of the combustion products is used to rotate the gas turbine. A significant part of this energy cannot be used by the gas turbine, so the products of combustion at the outlet of the gas turbine (exhaust gases) still carry a lot of heat with them (the temperature of the gases at the outlet of the gas turbine is about 500° WITH). In aircraft engines, this heat is wastefully released into the environment, but at the power unit under consideration it is used further - in the steam power cycle.To do this, the exhaust gases from the outlet of the gas turbine are "blown" from below into the so-called. "heat recovery boilers" - one for each gas turbine. Two gas turbines - two waste heat boilers.

Each such boiler is a structure several floors high.

In these boilers, the thermal energy of the gas turbine exhaust gases is used to heat water and turn it into steam. Subsequently, this steam is used when working in a steam turbine, but more on that later.

For heating and evaporation, water passes inside tubes with a diameter of about 30 mm, arranged horizontally, and the exhaust gases from the gas turbine "wash" these tubes outside. This is how heat is transferred from gases to water (steam):

Having given up most of the thermal energy to steam and water, the exhaust gases are at the top of the waste heat boiler and are removed using a chimney through the roof of the workshop:

From the outside of the building, chimneys from two waste heat boilers converge into one vertical chimney:

The following photos allow you to estimate the dimensions of the chimneys. The first photo shows one of the "corners" by which the chimneys of waste heat boilers are connected to the vertical shaft of the chimney, the rest of the photos show the process of installing the chimney.

But back to the design of waste heat boilers. The tubes through which water passes inside the boilers are divided into many sections - tube bundles, which form several sections:

1. Economizer section (which at this power unit has a special name - Gas Condensate Heater - GPC);

2. Evaporation section;

3. Superheating section.

The economizer section is used to heat water from a temperature of about 40°Cto a temperature close to the boiling point. After that, the water enters the deaerator - a steel container, where the parameters of the water are maintained such that the gases dissolved in it begin to be intensively released from it. The gases are collected at the top of the tank and vented to the atmosphere. The removal of gases, especially oxygen, is necessary to prevent rapid corrosion of the process equipment with which our water comes into contact.

After passing the deaerator, the water acquires the name "feed water" and enters the feed pumps. This is what the feed pumps looked like when they were just brought to the station (there are 3 of them in total):

Feed pumps are electrically driven (asynchronous motors are powered by a voltage of 6kV and have a power of 1.3MW). Between the pump itself and the electric motor there is a hydraulic coupling - the unit,allows you to smoothly change the speed of the pump shaft over a wide range.

The principle of operation of the fluid coupling is similar to the principle of operation of the fluid coupling in automatic transmissions of cars.

Inside there are two wheels with blades, one "sits" on the motor shaft, the second - on the pump shaft. The space between the wheels can be filled with oil at different levels. The first wheel, rotated by the engine, creates a flow of oil that "hit" the blades of the second wheel, and entraining it in rotation. The more oil is filled between the wheels, the better the "cohesion" will be between the shafts, and the greater the mechanical power will be transmitted through the fluid coupling to the feed pump.

The oil level between the wheels is changed using the so-called. "scoop pipe", pumping oil from the space between the wheels. Regulation of the position of the scoop pipe is carried out using a special actuator.

The feed pump itself is centrifugal, multi-stage. Note that this pump develops the full pressure of the steam turbine steam and even exceeds it (by the value of the hydraulic resistance of the remaining part of the waste heat boiler, hydraulic resistance of pipelines and fittings).

The design of the impellers of the new feed pump could not be seen (because it had already been assembled), but parts of the old feed pump of a similar design were found on the territory of the station. The pump consists of alternating rotating centrifugal wheels and fixed guide discs.

Fixed guide disc:

Impellers:

From the outlet of the feed pumps, feed water is supplied to the so-called. "separator drums" - horizontal steel tanks designed to separate water and steam:

Each waste heat boiler is equipped with two separator drums (4 in total at the power unit). Together with the tubes of the evaporator sections inside the waste heat boilers, they form the circulation circuits of the steam-water mixture. It works as follows.

Water with a temperature close to the boiling point enters the tubes of the evaporator sections, flowing through which it is heated to the boiling point and then partially turns into steam. At the outlet of the evaporation section, we have a steam-water mixture, which enters the separator drums. Special devices are mounted inside the separator drums

which help to separate the steam from the water. The steam is then fed to the superheating section, where its temperature increases even more, and the water separated in the separator drum (separated) is mixed with feed water and again enters the evaporative section of the waste heat boiler.

After the superheating section, steam from one waste heat boiler is mixed with the same steam from the second waste heat boiler and enters the turbine. Its temperature is so high that the pipelines through which it passes, if thermal insulation is removed from them, glow in the dark with a dark red glow. And now this steam is fed to the steam turbine in order to give up part of its thermal energy in it and do useful work.

The steam turbine has 2 cylinders - a high pressure cylinder and a low pressure cylinder. Low pressure cylinder - double flow. In it, the steam is divided into 2 streams operating in parallel. The cylinders contain the turbine rotors. Each rotor, in turn, consists of stages - disks with blades. "Hitting" the blades, the steam causes the rotors to rotate. The photo below reflects general design steam turbine: closer to us - a high pressure rotor, farther from us - a two-flow low pressure rotor

This is what the low pressure rotor looked like when it was just unpacked from the factory packaging. Notice it only has 4 steps (not 8):

And here is the high pressure rotor on closer inspection. It has 20 steps. Also pay attention to the massive steel casing of the turbine, consisting of two halves - the lower and upper (only the lower one in the photo), and the studs with which these halves are connected to each other. In order to make the case faster at start-up, but at the same time, warm up more evenly, a steam heating system of "flanges and studs" is used - do you see a special channel around the studs? It is through it that a special steam flow passes to warm up the turbine casing during its start-up.

In order for the steam to "hit" the rotor blades and make them rotate, this steam must first be directed and accelerated in the right direction. For this, the so-called. nozzle arrays - fixed sections with fixed blades, placed between the rotating disks of the rotors. The nozzle arrays DO NOT rotate - they are NOT movable, and serve only to direct and accelerate the steam in the desired direction. In the photo below, steam passes "behind these blades at us" and "unwinds" around the axis of the turbine counterclockwise. Further, "hitting" the rotating blades of the rotor discs, which are located immediately behind the nozzle grate, the steam transfers its "rotation" to the turbine rotor.

In the photo below you can see the parts of the nozzle arrays prepared for installation.

And in these photos - lower part Turbine housing with nozzle array halves already installed in it:

After that, the rotor is "embedded" into the housing, the upper halves of the nozzle arrays are mounted, then the upper part of the housing, then various pipelines, thermal insulation and casing:

After passing through the turbine, the steam enters the condensers. This turbine has two condensers - according to the number of flows in the low pressure cylinder. Look at the photo below. It clearly shows the lower part of the steam turbine housing. Pay attention to the rectangular parts of the low pressure cylinder body, closed on top with wooden shields. These are steam turbine exhausts and condenser inlets.

When the steam turbine housing is fully assembled, a space is formed at the outlets of the low-pressure cylinder, the pressure in which during the operation of the steam turbine is about 20 times lower than atmospheric pressure, therefore the low-pressure cylinder housing is designed not for pressure resistance from the inside, but for pressure resistance from the outside - i.e. e. atmospheric pressure air. The condensers themselves are under the low pressure cylinder. In the photo below, these are rectangular containers with two hatches on each.

The condenser is arranged similarly to the waste heat boiler. Inside it is a lot of tubes with a diameter of about 30mm. If we open one of the two hatches of each condenser and look inside, we will see "tube boards":

Cooling water, which is called process water, flows through these tubes. Steam from the exhaust of a steam turbine is in the space between the tubes outside them (behind the tube plate in the photo above), and, giving off residual heat to process water through the walls of the tubes, condenses on their surface. The steam condensate flows down, accumulates in the condensate collectors (at the bottom of the condensers), and then enters the condensate pumps. Each condensate pump (and there are 5 in total) is driven by a three-phase asynchronous electric motor, designed for a voltage of 6 kV.

From the outlet of the condensate pumps, water (condensate) again enters the inlet of the economizer sections of the waste heat boilers and, thereby, the steam-power cycle is closed. The whole system is almost hermetic and the water, which is the working fluid, is repeatedly converted into steam in waste heat boilers, in the form of steam it does work in the turbine in order to turn back into water in the turbine condensers, etc.

This water (in the form of water or steam) is constantly in contact with the internal parts of the process equipment, and in order not to cause their rapid corrosion and wear, it is chemically prepared in a special way.

But back to the steam turbine condensers.

Industrial water, heated in the tubes of the steam turbine condensers, is removed from the workshop through underground industrial water supply pipelines and fed to the cooling towers in order to transfer the heat taken from the steam from the turbine to the surrounding atmosphere. The photographs below show the design of the cooling tower built for our power unit. The principle of its operation is based on the spraying of warm technical water inside the cooling tower with the help of shower devices (from the word "shower"). Water droplets fall down and give off their heat to the air inside the cooling tower. The heated air rises, and in its place from the bottom of the cooling tower comes cold air from the street.

This is what the cooling tower looks like at its base. It is through the "slit" at the bottom of the cooling tower that cold air enters to cool the process water.

At the bottom of the cooling tower there is a catchment basin, where droplets of process water fall and collect, released from the choking devices and giving up their heat to the air. Above the pool there is a system of distribution pipes, through which warm technical water is supplied to showering devices.

The space above and below the showering devices is filled with a special stuffing of plastic blinds. The lower louvers are designed to more evenly distribute the "rain" over the area of ​​the cooling tower, and the upper louvers are designed to trap small droplets of water and prevent excessive entrainment of technical water along with air through the top of the cooling tower. However, at the time the photographs were taken, the plastic shutters had not yet been installed.

Bo" The highest part of the cooling tower is not filled with anything and is intended only for creating draft (heated air rises). If we stand above the distribution pipelines, we will see that there is nothing above and the rest of the cooling tower is empty

The following video captures the experience of being inside the cooling tower

At the time when the photos of this page were taken, the cooling tower built for the new power unit was not yet operational. However, there were other cooling towers in operation on the territory of this CHP plant, which made it possible to capture a similar cooling tower in operation. Steel louvres at the bottom of the cooling tower are designed to regulate the flow of cold air and prevent overcooling of process water in winter

The process water cooled and collected in the cooling tower basin is again fed to the inlet of the steam turbine condenser tubes in order to take a new portion of heat from the steam, etc. In addition, process water is used to cool other process equipment, such as electric generators.

The following video shows how process water is cooled in a cooling tower.

Since industrial water is in direct contact with the surrounding air, dust, sand, grass and other dirt get into it. Therefore, at the inlet of this water to the workshop, on the inlet pipeline of technical water, a self-cleaning filter is installed. This filter consists of several sections mounted on a rotating wheel. Through one of the sections, from time to time, a reverse flow of water is organized for washing it. The section wheel then turns and the next section is flushed, and so on.

This is what this self-cleaning filter looks like from the inside of the process water pipeline:

And so outside (the drive motor has not yet been mounted):

Here we should make a digression and say that the installation of all process equipment in the turbine shop is carried out using two overhead cranes. Each crane has three separate winches designed to handle loads of different weights.

Now I would like to tell a little about the electrical part of this power unit.

Electricity is generated by three electric generators driven by two gas turbines and one steam turbine. Part of the equipment for the installation of the power unit was brought by road, and part by rail. A railroad was laid right into the turbine shop, along which large-sized equipment was transported during the construction of the power unit.

The photo below shows the delivery of the stator of one of the generators. Let me remind you that each electric generator has a rated electric power of 150 MW. Note that the railway platform on which the generator stator was brought has 16 axles (32 wheels).

The railway has a slight rounding at the entrance to the workshop, and given that the wheels of each wheel pair are rigidly fixed on their axles, when driving on a rounded section of the railway, one of the wheels of each wheel pair is forced to slip (because the rails on the rounding have different length). The video below shows how this happened when the platform was moving with the stator of the power generator. Pay attention to how the sand on the sleepers bounces when the wheels slip along the rails.

Due to the large mass, the installation of the stators of electric generators was carried out using both overhead cranes:

The photo below shows an internal view of the stator of one of the generators:

And this is how the installation of the rotors of electric generators was carried out:

The output voltage of the generators is about 20 kV. The output current is thousands of amperes. This electricity is taken from the turbine shop and fed to step-up transformers located outside the building. To transfer electricity from power generators to step-up transformers, the following electrical wires are used (current flows through a central aluminum pipe):

To measure the current in these "wires", the following current transformers are used (in the third photo above, the same current transformer stands vertically):

The photo below shows one of the step-up transformers. Output voltage - 220 kV. From their outlets, electricity is fed into the power grid.

In addition to electrical energy, the CHPP also generates thermal energy used for heating and hot water supply of nearby areas. For this, steam extractions are made in the steam turbine, i.e., part of the steam is removed from the turbine without reaching the condenser. This, still quite hot steam, enters the network heaters. The network heater is a heat exchanger. It is very similar in design to a steam turbine condenser. The difference is that it is not technical water that flows in the pipes, but network water. There are two network heaters at the power unit. Let's look again at the photo with the turbine capacitors. Rectangular containers are capacitors, and "round" ones - this one is exactly network heaters. I remind you that all this is located under the steam turbine.

The network water heated in the pipes of network heaters is supplied through underground pipelines of network water to the heating network. Heating the building of the districts located around the CHPP, and having given them its heat, the network water returns to the station again to be heated again in the network heaters, etc.

The operation of the entire power unit is controlled by the automated process control system "Ovation" of the American corporation "Emerson"

And here is how the cable mezzanine, located under the APCS room, looks like. Through these cables, the process control system receives signals from a variety of sensors, as well as signals to actuators.

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What are the reasons for the introduction of CCGT in Russia, why is this decision difficult but necessary?

Why did they start building a CCGT

The decentralized market for the production of electricity and heat dictates the need for energy companies to increase the competitiveness of their products. The main importance for them is the minimization of investment risk and the real results that can be obtained using this technology.

The abolition of state regulation in the electricity and heat market, which will become a commercial product, will lead to increased competition between their producers. Therefore, in the future, only reliable and highly profitable power plants will be able to provide additional capital investments in the implementation of new projects.

CCGT selection criteria

The choice of one or another type of CCGT depends on many factors. One of the most important criteria in the implementation of the project is its economic viability and safety.

An analysis of the existing market for power plants shows a significant need for inexpensive, reliable in operation and highly efficient power plants. The modular, pre-configured design of this concept makes the plant highly adaptable to any local conditions and specific customer requirements.

Such products satisfy more than 70% of customers. These conditions are largely met by GT and SG-TPPs of the utilization (binary) type.

Energy dead end

An analysis of the Russian energy sector, carried out by a number of academic institutions, shows that even today the Russian electric power industry is practically losing 3-4 GW of its capacities annually. As a result, by 2005, according to RAO "UES of Russia", the volume of equipment that has worked out its physical resource will amount to 38% of the total capacity, and by 2010 this figure will already be 108 million kW (46%).

If events develop exactly according to this scenario, then most of the power units due to aging in the coming years will enter the zone of a serious risk of accidents. The problem of technical re-equipment of all types of existing power plants is exacerbated by the fact that even some of the relatively “young” 500-800 MW power units have exhausted the service life of the main units and require serious restoration work.

Read also: The importance of capital in the design of a combined cycle plant

Reconstruction of power plants is easier and cheaper

Extending the life of plants with the replacement of large components of the main equipment (turbine rotors, heating surfaces of boilers, steam pipelines), of course, is much cheaper than building new power plants.

It is often convenient and profitable for power plants and manufacturing plants to replace equipment with a similar one that is being dismantled. However, this does not take advantage of the opportunities to significantly increase fuel economy, does not reduce pollution environment, modern means of automated systems of new equipment are not used, the costs of operation and repair increase.

Low efficiency of power plants

Russia is gradually entering the European energy market, joining the WTO, but at the same time, we have had an extremely difficult situation for many years. low level thermal efficiency of electric power industry. Average level the efficiency of power plants when operating in the condensing mode is 25%. This means that if the price of fuel rises to the world level, the price of electricity in our country will inevitably become one and a half to two times higher than the world price, which will affect other goods. Therefore, the reconstruction of power units and thermal stations should be carried out in such a way that the new equipment being introduced and individual components of power plants are at the modern world level.

Energy chooses combined cycle technologies

Now, despite the hard financial position, in the design bureaus of power engineering and aircraft engine research institutes, the development of new equipment systems for thermal power plants was resumed. In particular, we are talking on the creation of condensing steam-gas power plants with an efficiency of up to 54-60%.

Economic assessments made by various domestic organizations indicate a real opportunity to reduce the costs of electricity production in Russia if such power plants are built.

Even simple gas turbines will be more efficient in terms of efficiency

At CHPPs, it is not necessary to universally use CCGTs of this type, such as CCGT-325 and CCGT-450. Circuit solutions may be different depending on specific conditions, in particular, on the ratio of thermal and electrical loads.

Read also: How to choose a gas turbine plant for a CCGT plant

In the simplest case, when using the heat of gases exhausted in gas turbines for heat supply or production of process steam, the electric efficiency of CHPPs with modern gas turbines will reach a level of 35%, which is also significantly higher than those existing today. About the differences in the efficiency of GTU and PTU - read in the article How the efficiency of GTU and CCGT efficiency differ for domestic and foreign power plants

The use of gas turbines in thermal power plants can be very wide. Currently, about 300 steam turbine units of CHPP with a capacity of 50-120 MW are fed with steam from boilers that burn 90 percent or more natural gas. In principle, all of them are candidates for technical re-equipment using gas turbines with a unit capacity of 60-150 MW.

Difficulties with the introduction of GTU and CCGT

However, the process of industrial introduction of GTU and CCGT in our country is extremely slow. The main reason is investment difficulties associated with the need for sufficiently large financial investments in the shortest possible time.

Another limiting circumstance is related to the actual absence in the range of domestic manufacturers of purely power gas turbines that have been proven in large-scale operation. GTUs of a new generation can be taken as prototypes of such gas turbines.

Binary CCGT without regeneration

Binary CCGTs have a certain advantage, as they are the cheapest and most reliable in operation. The steam part of binary CCGTs is very simple, since steam regeneration is unprofitable and is not used. The temperature of the superheated steam is 20-50 °C lower than the temperature of the exhaust gases in the gas turbine. At present, it has reached the standard level in the energy sector of 535-565 °С. The live steam pressure is chosen so as to provide acceptable humidity in the last stages, the operating conditions and blade sizes of which are approximately the same as in powerful steam turbines.

Influence of steam pressure on the efficiency of CCGT

Of course, economic and cost factors are taken into account, since the steam pressure has little effect on the thermal efficiency of the CCGT. In order to reduce the temperature differences between the gases and the steam-water medium and to use the heat of the gases exhausted in the gas turbine in the best way with less thermodynamic losses, the evaporation of the feed water is organized at two or three pressure levels. The steam generated at reduced pressures is mixed in at intermediate points of the flow path of the turbine. Steam reheating is also carried out.

Read also: Choice of the cycle of the combined cycle plant and the circuit diagram of the CCGT

Influence of flue gas temperature on CCGT efficiency

With an increase in the gas temperature at the turbine inlet and outlet, the steam parameters and the efficiency of the steam part of the GTP cycle increase, contributing to the overall increase in the CCGT efficiency.

The choice of specific directions for the creation, improvement and large-scale production of power machines should be decided taking into account not only thermodynamic perfection, but also the investment attractiveness of projects. The investment attractiveness of Russian technical and production projects for potential investors is the most important and the most urgent problem, on the solution of which the revival of the Russian economy largely depends.

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